High voltage electron discharge tube

ABSTRACT

A HIGH VOLTAGE ELECTRON TUBE, SUCH AS TYPE 6BK4, HAS A CATHODE AND A TUBULAR ANODE HAVING AN ELECTRON TARGET THEREWITHIN. A PORT IS PROVIDED THROUGH THE ANODE WALL TO FACILITATE OUTGASSING OF THE ANODE. A PORTION OF THE ANODE   WALL ADJACENT TO THE PORT EXTENDS INWARDLY OF THE ANODE INTO THE PATH OF X-RADIATIONS FROM THE TARGET TO THE PORT.

United States Patent [56} References Cited UNITED STATES PATENTS 2,813,209 11/1957 Byram etal 313/356X 2,813,215 11/1957 Reichert 313/356X 3,041,494 6/1962 Lough et a1 3 l3/356X Primary Examiner-David Schonberg Assistant Examiner-Paul A. Sacher Attorney-Glenn H. Bruestle ABSTRACT: A high voltage electron tube, such as type 68104, has a cathode and a tubular anode having an electron target therewithin. A port is provided through the anode wall to facilitate outgassing of the anode. A portion of the anode wall adjacent to the port extends inwardly of the anode into the path of X-radiations from the target to the port.

HIGH VOLTAGE ELECTRON DISCHARGE TUBE BACKGROUND OF THE INVENTION This invention related to high voltage electron discharge devices.

One type of high voltage device, e.g., the RCA 6BR 4voltage regulator tube, includes an anode comprising an elongated tubular member having open and closed ends, and an electron target within the member extending transversely thereof and segmenting the member into two portions. In the fabrication of such devices, it is the practice to outgas the metal parts of the device by radiofrequency induction heating, while exhausting the device envelope through a tubulation. To allow exhausting of gasses from within the anode, and especially from the space between the electron target and closed end of the member, the wall of the anode member is provided with exhaust ports.

In operation of the device, electrons impact upon the anode target with great energy, thereby producing X-radiations. It is found that some of these radiations escape from the anode through the anode exhaust ports. This is undesirable as giving rise to a possible health hazard.

SUMMARY OF THE INVENTION A high voltage tube comprises an anode including an electron target. The wall of the anode has an exhaust port therethrough, and means are provided shielding radiations along rectilinear paths from said target through the exhaust port.

DESCRIPTION OF THE DRAWING FIG. I is a side view, partly broken away, of an electron made in accordance with the present invention; and

FIG. 2 is a section, on an enlarged scale, taken along line 2-2 of FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENT The illustrative tube 3 shown in the drawing is a standard RCA 68K 4voltage regulator with the exception of the anode electrode.

The tube 3 comprises a glass envelope 4 and a base 6. Terminals 8 extend through the base 6 and into electrical contact with a cathode l and a grid electrode 11 disposed within a shield member l2. The shield member 12 has an opening 14 through the upper surface thereof, allowing egress of a beam of electrons from the cathode during operation of the tube.

Disposed in longitudinally spaced relation with the shield 12 is an elongated three-part tubular anode electrode comprising two cylinders 22 and 24, and a terminal member 216. The lower cylinder 22 has an open end 28, and has, at the other end thereof, an annular flange 32. The upper cylinder 24 has, at its lower end, and annular flange 36. Disposed between the two cylinders 22 and 24, and perpendicular to the longitudinal axes thereof, is a disclike electron target 40. The target 40 is clamped between the two flanges 32 and 36 of the two cylinders 22 and 24, respectively, and the two cylinders are secured together by means of the flange 32 of the cylinder 22 being clamped around the flange 36 of the upper cylinder 24.

The upper end 44 of the cylinder 24 is closed, and the terminal member 26 is secured to the closed end 44, as by welding or crimping. The terminal member 26 extends outwardly through, in sealed relation with, the upper end of the glass envelope In the fabrication of discharge devices of the type in question, and in accordance with known procedures, the device metal portions are heated, e.g., by radiofrequency induction heating, to degas the parts. Because the portion of the anode between the electron target and the closed upper end of the anode cylinder is substantially a completely enclosed space, openings or ports are normally provided through the wall of the anode cylinder to allow exhausting of the gasses generated therein during the outgassing step.

In some instances, it is noted, the upper end of the anode cylinder as well as the wall of the anode terminal member have openings therethrough the further facilitate outgassing of the metal ports. Even in such instances, however, exhaust ports are generally used to facilitate outgassing of what is still a substantially completely enclosed space.

I-Ieretofore, the exhaust ports were simply circular apertures through the anode sidewall. It has recently been discovered, however, that during operation of the device, during which X-radiations are produced at the target resulting from the target being bombarded by electrons from the cathode, a portion of the X-radiations escape from the anode through the exhaust ports. This is undesirable.

To prevent such escape of potentially harmful radiations in the present novel device 3, port shielding means 48 are provided which preferably comprise portions of the anode wall adjacent to the exhaust ports 50 which are disposed inwardly of the cylinder 24 into the path of radiations from the target to the ports. The shielding means or elements 48 are such as to obstruct radiation from the target 40 along line-of-sight paths through the ports 50. In such preferred embodiment, the ports 50 are produced as a result of striking and forming the shielding elements 48 from the anode wall.

In a preferred embodiment, the shielded port 50 is provided as follows. Prior to the assembly of the anode into an integral member, one or more narrow slits, e.g., having a width in the order of 5mils, and a length of about 200mils, are formed through the cylinder 24 wall at right angles to the cylinder longitudinal axis. Using a half round punch, and a back up mandrel within the cylinder, a portion 48 of the cylinder wall defining the lower edge 54 of the slit, that is, the side of the slit nearest the lower open end of the cylinder 24, is deformed inwardly into a generally semiconical or scooplike shape. The exhaust port 50 thus provided has upper and lower edges 56 and 54, respectively, which are parallel to one another and which lie in a substantially common plane parallel to the plane of the target 40. With a spacing between the points of maximum spacing of the two edges 54 and 56 of about mils, a sufficiently large opening is provided for efficient exhausting of gasses from the cylinder. Most importantly, the deformed portion 48 of the cylinder wall substantially completely shields the exhaust port opening 50 from radiations following rectilinear paths from the electron target 40 to the exhaust ports. The more narrow the starting slit, and the more substantially coplanar the port edges 54 and 56, and the more effective is the shielding.

In one series of tests, the level of radiation at the exhaust ports of conventional 6BR 4 tubes, in which the exhaust ports are simple circular cutouts through the anode wall, was as high as 6milli-Roentgens/hr. The level of radiation at the exhaust ports of otherwise conventional 6 BK 4 tubes having port shielding means of the type described herein was not greater than 0.3 milli-Roentgens/hr. Thus, the reduction in radiation is in the order of 20 to l.

I claim:

1. A high voltage electron discharge device comprising an envelope including therein:

a source of electrons,

A tubular anode spaced from said electron source including an electron target therewithin, said target being a source of radiations when bombarded by electrons,

said target and a wall portion of said anode defining an enclosed space, said wall portion having an exhaust port therethrough, and

means integral with said wall portion proximate said port providing shielding of radiations along rectilinear paths from said target through said port.

2. An electron discharge device as in claim I wherein said shielding means comprises and element partially struck from said wall and extending out of the normal contour of said wall.

3. An electron discharge device as in claim 2 wherein said element extends interiorly of said space.

4. An electron discharge device comprising an envelope including therein:

an electron source for emitting electrons along a path;

the edge of said portion lying in a plane substantially parallel to the plane of said target, whereby said portion blocks the escape of rations from said target through said opening.

5. An electron discharge device as in claim 4 wherein said wall portion has a generally scooplike shape including an arcuate edge, and the opposite edges of the wall portions defining said opening are substantially coplanar. 

